Ultrasonic surgical instruments, including both hollow core and solid core instruments, are used for the safe and effective treatment of many medical conditions. Ultrasonic surgical instruments, and particularly solid core ultrasonic surgical instruments, are advantageous because they may be used to cut and/or coagulate tissue using energy in the form of mechanical vibrations transmitted to a surgical end effector at ultrasonic frequencies. Ultrasonic vibrations, when transmitted to tissue at suitable energy levels and using a suitable end effector, may be used to cut, dissect, coagulate, elevate or separate tissue. Ultrasonic surgical instruments utilizing solid core technology are particularly advantageous because of the amount of ultrasonic energy that may be transmitted from the ultrasonic transducer, through an ultrasonic transmission waveguide, to the surgical end effector. Such instruments may be used for open procedures or minimally invasive procedures, such as endoscopic or laparoscopic procedures, wherein the end effector is passed through a trocar to reach the surgical site.
Activating or exciting the end effector (e.g., cutting blade, ball coagulator) of such instruments at ultrasonic frequencies induces longitudinal vibratory movement that generates localized heat within adjacent tissue, facilitating both cutting and coagulating. Because of the nature of ultrasonic surgical instruments, a particular ultrasonically actuated end effector may be designed to perform numerous functions, including, for example, cutting and coagulating.
Ultrasonic vibration is induced in the surgical end effector by electrically exciting a transducer, for example. The transducer may be constructed of one or more piezoelectric or magnetostrictive elements in the instrument hand piece. Vibrations generated by the transducer section are transmitted to the surgical end effector via an ultrasonic waveguide extending from the transducer section to the surgical end effector. The waveguides and end effectors are designed to resonate at the same frequency as the transducer. When an end effector is attached to a transducer the overall system frequency may be the same frequency as the transducer itself. The transducer and the end effector may be designed to resonate at two different frequencies and when joined or coupled may resonate at a third frequency. The zero-to-peak amplitude of the longitudinal ultrasonic vibration at the tip, d, of the end effector behaves as a simple sinusoid at the resonant frequency as given by:d=A sin(ωt)    where: ω=the radian frequency which equals 2π times the cyclic frequency, f; and    A=the zero-to-peak amplitude.The longitudinal excursion is defined as the peak-to-peak (p-t-p) amplitude, which is just twice the amplitude of the sine wave or 2 A.
Solid core ultrasonic surgical instruments may be divided into two types, single element end effector devices and multiple-element end effectors. Single element end effector devices include a variety of blade types such as ball, hooked, curved, and coagulating shears. Single-element end effector instruments have limited ability to apply blade-to-tissue pressure when the tissue is soft and loosely supported. Substantial pressure may be necessary to effectively couple ultrasonic energy to the tissue. The inability of a single-element end effector to grasp the tissue results in a further inability to fully coapt tissue surfaces while applying ultrasonic energy, leading to less-than-desired hemostasis and tissue joining. Multiple-element end effectors include a clamping mechanism comprising a clamp arm that works in conjunction with the vibrating blade to form a jaw like structure. Ultrasonic clamping coagulators provide an improved ultrasonic surgical instrument for cutting/coagulating tissue, particularly loose and unsupported tissue. The clamping mechanism presses the tissue against the vibrating ultrasonic blade and applies a compressive or biasing force against the tissue to achieve faster cutting and hemostasis (e.g., coagulation) of the tissue with less attenuation of blade motion.
As an alternative to open surgical procedures, many modern surgeons use endoscopes and endoscopic instruments to remotely access organs through smaller, puncture-like incisions. As a direct result thereof, patients tend to benefit from less scarring and reduced healing time. Endoscopic instruments are inserted into the patient through a cannula, or port, which has been made with a trocar. Typical sizes for cannulas range from three millimeters to twelve millimeters. Smaller cannulas are usually preferred. However, the smaller cannulas in turn present additional challenges in the design of the endoscopic instruments that fit through the smaller cannulas. Many endoscopic surgical procedures require cutting or ligating blood vessels or vascular tissue as well as grasping, cutting, dissecting, coagulating, elevating, manipulating, and/or separating tissue.
For the purposes herein, “coagulation” is defined as a process of desiccating tissue wherein the tissue cells are ruptured and dried. “Vessel sealing” or “tissue sealing” is defined as the process of liquefying the collagen in the tissue so that it reforms into a fused mass. Coagulation of small vessels is sufficient to permanently close them, while larger vessels need to be sealed to assure permanent closure. Tissue welding is a technique for closing wounds and vessels and is applied in many surgical specialties. Tissue welding is a technique for closing wounds by creating a hemostatic seal in the wounds or vessels as well as creating strong anastomoses in the tissue. Ultrasonic surgical instruments may be employed to achieve hemostasis with minimal lateral thermal damage to the tissue. The hemostasis or anastomoses occurs through the transfer of mechanical energy to the tissue. Internal cellular friction breaks hydrogen bonds resulting in protein denaturization. As the proteins are denatured at temperatures below 100° C., a sticky coagulum forms and seals small vessels. Anastomoses occurs when the effects are prolonged. Thus, the ultrasonic energy in the vibrating blade may be employed to create hemostatic seals in vessels and adjacent tissues in wounds and to create strong anastomoses in tissue. Ultrasonic vibrating single or multiple end effectors, either alone or in combination with clamping mechanisms, produce adequate mechanical energy to seal vessels regardless of the temperature of the end effector and/or the tissue. To create strong anastomoses of the tissue, the temperature of the end effector and the tissue should be maintained below approximately 50° C. to allow for the creation of a coagulum to seal the tissues together without desiccating the tissues.
In the design of medical instruments, several factors may be applied to assess the viability of the ergonomics of a particular design. One factor of ergonomics is comfort. Comfort may be characterized by the ability to manipulate and control the device without undue muscle strain, pressure points, or other harmful ergonomic effects. Comfort is created from properly sized features located to fit the anatomy of the user, and adequate distribution of force against the user's body. The ability to use an instrument over an extended period without fatigue, pain, or loss of precision is a measure of comfort. Another factor of ergonomics is the ability to use an instrument over an extended time period without fatigue, pain, or loss of precision is a measure of comfort. Aside from comfort, one objective factor is the ability to control the working end of the device with the degree of control needed to accomplish the surgical task with ease. The extent that this control may be achieved emanates first from the inherent stability of the instrument in the hand of the user, and second from the ability to perform finer motions in order to manipulate the specific instrument controls. Design efforts balance the ability to achieve overall stability in the hand while facilitating appropriate access and mobility to utilize the fine controls. The stability of the surgical instrument in the hand may be accomplished via a variety of grips. Common grips include ring handles, in-line scissors, and pistol configurations, among others. Pistol grips generally provide points of fixation on the hand:
(1) A point between the thumb and index finger resting in the web of the joint;
(2) A grasping force between the thumb and index finger; and
(3) A gripping force between the fingers and the palm when activating a trigger, power switch, knob, lever, or other feature.
Due to the inherent spatial considerations of the surgical cavity, surgeons often have difficulty performing traditional surgical methods using endoscopic instruments inserted into the patient through a cannula. The spatial limitations, coupled with the multi-function capability of many endoscopic instruments, particularly laparoscopic ultrasonic surgical instruments, create ergonomic challenges for the surgeon to easily access and operate the multiple functions and controls of the instrument. Many ultrasonic surgical instruments with multiple-element end effectors require a high force of the jaws of the clamping mechanism, which in turn requires higher input forces at the handle/trigger. This creates challenges in providing a comfortable handle/trigger interface for the user. Just as important is to enable the surgeon to finely control the opening motion of the jaws to facilitate fine dissection without creating fatigue or pressure points on the surgeon's hands. Activating electrical power switches on the ultrasonic instrument housing also presents a challenge. A surgeon needs to easily access any of the switches at any point while also avoiding inadvertent or unintentional activation at any time. Other functions that a surgeon may need to perform include rotating the shaft, or selecting power levels. In addition, the user should be able to operate any of these functions without looking, allowing them to focus entirely on the monitor view during a laparoscopic procedure. In addition, it may be desirable for the user not to have to reposition their grip in order to operate any of these key functions the power switches, and be able to easily manipulate the clamp force or power levels while opening the jaws of the clamping mechanism of the end effector.
Other ergonomic challenges presented by conventional laparoscopic ultrasonic surgical instruments include the ability of the user to easily access and operate multiple functions, sometimes simultaneously. Typically the index finger is used to operate a rotation knob located at the distal end of the device handle to rotate the shaft. However, controlling the power buttons/switches also employs the use of the index finger, creating an inherent challenge for locating the rotation knob and the switches on the housing such that they both may be reached by the index finger. Ultrasonic devices include multiple controls such as shaft rotation, power settings, and trigger closure that must be accessible in various hand positions and for many hand sizes.
Traditional laparoscopic ultrasonic surgical instruments usually have a rotation control knob located at the distal end of the instrument that can be accessed with the index finger to rotate the shaft. However, controlling the power buttons/switches also employs the use of the index finger, creating an inherent challenge for locating the rotation knob and the switches on the housing such that they both may be reached by the index finger. The finger tip rotation control often may be difficult to reach for a surgeon with small hands especially when the instrument is oriented in positions at extreme angles or orientations that may be necessary to position the tip of the instrument in proximity to the anatomy to be treated.
With respect to hand size, it has long been a challenge to create laparoscopic ultrasonic surgical instruments with a handle design in terms of size, shape, and location of control interfaces that is “ideal” for everyone. The very large disparity of anthropometrics from small females to large males traditionally creates challenges for users at the extreme ends of the spectrum. Although instruments having various different sized handles to accommodate the disparity in hand sizes have been considered, purchasers generally desire to carry fewer inventories, and thus multiple variations have not been accepted. In addition, there is always the risk that a certain sized handle may not be available to a particular doctor at a particular hospital.
The multi-function capability of many ultrasonic surgical instruments, particularly laparoscopic ultrasonic surgical instruments, create ergonomic challenges in the ability of the user to comfortably access and operate the multiple functions and controls of the instrument. This include, for example, the ability to comfortably actuate the jaws of the clamping mechanism and activate the hand control buttons/switches, sometimes simultaneously. The user should be able to control the opening motion of the end effectors to facilitate spreading dissection. Laparoscopic handle interface designs traditionally incorporate a “scissor” type ring to allow for this outward motion, using outward movement of the thumb to oppose the “anchored” fingers. However, this does not provide optimal control of the tip. Some conventional ultrasonic surgical instruments may comprise a pistol grip that incorporates a trigger that is pushed outward with the index and middle fingers of the user while maintaining a grip on the handle stock, however, this may create fatigue and hand strain. This outward motion, however, may be necessary when doing fine dissection during a laparoscopic procedure. The pistol grip style handle provides comfort, ease, and stability to the surgeon. The conventional pistol grip style handle may not be optimum, however, for dissection, where many surgeons prefer a scissor grip style design instead.
Accordingly, there is a need for an ergonomic handle assembly for an ultrasonic surgical instrument that provides the ability of the user to comfortably access and operate multiple functions. In addition, there is a need for a handle assembly for an ultrasonic surgical instrument that enables a user to comfortably actuate the jaws of the clamping mechanism and activate the hand control buttons/switches. There is also a need to optimize the handle assemblies in terms of ergonomic comfort, stability, and controllability for a large range of hand sizes.